This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-287389, filed Sep. 21, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention generally relates to a perpendicular magnetic recording method disk drive, and in particular a disk drive provided with a function of realizing the stabilization of a soft magnetic layer of a disk medium.
2. Description of the Related Art
In recent years, in the field of a disk drive represented by a hard disk drive, as a technology for exceeding a limit of a recording density in the longitudinal magnetic recording method, a perpendicular magnetic recording method is noted. In this perpendicular magnetic recording method, the realization of a disk drive using a disk medium (hereinafter, simply referred to as a disk) which has a double-layered structure as a recording medium is promoted.
A disk having the double-layered structure has a magnetic recording layer showing a magnetic anisotropy in a perpendicular direction, and a soft magnetic layer between the recording magnetic layer and a substrate. The soft magnetic layer has a function of allowing some of the magnetic flux generated from one of the magnetic poles of the head to pass to the other magnetic pole at the time of a data recording operation, supporting a recording operation of the head.
By the way, it has been confirmed that magnetic noise is likely to be generated in the soft magnetic layer from instability in the magnetic domain state. In particular, when the head moves on the disk, a spike (or a pulse) magnetic noise is likely to be generated from the soft magnetic layer which comes close to the head. This magnetic noise affects the recording magnetic layer so that the reproduction signal level from the head is lowered. Furthermore, the soft magnetic layer has a high sensitivity against a disturbance magnetic field, which constitutes a factor of generating a destabilization of the magnetic state of the recording magnetic layer.
In order to make an attempt of realizing a disk drive of a perpendicular magnetic recording method using a double-layered structure disk, it is indispensable to take measures of suppressing the generation of magnetic noises from the soft magnetic layer while suppressing instability of the magnetic domain state in the above soft magnetic layer.
There is proposed a constitution of a casing of a disk drive of ferromagnetic substance material, in particular, for the realization of a shield function with respect to a disturbance magnetic field. (See, for example, U.S. Pat. No. 5,654,847). However, in this proposed method, the instability of the soft magnetic layer with respect to the disturbance magnetic field can be suppressed, but the shield function is weak against the magnetic field (floating magnetic field) generated from the inside of the disk drive, and the instability of the magnetic domain state of the soft magnetic layer cannot be settled.
Furthermore, as another proposal, there is proposed a disk structure in which a hard magnetic pinning layer is provided which has uniform magnetization which is exchange connected to the soft magnetic layer on the lower layer of the soft magnetic layer. (For example, see Japanese Patent Publication No. 2,947,029.) In such a disk structure, there is a possibility that endurance against a disturbance magnetic field can be improved, and the stabilization of the magnetic domain state of the soft magnetic layer can be stabilized. However, the uniforming step of magnetization with respect to the hard magnetic pinning layer becomes necessary. Furthermore, the thickness of the structure layer of the disk becomes extremely thick. This makes it particularly hard to manufacture.
Furthermore, there is proposed a disk drive which uses a magnetic head having a magnetic field generation device for applying a magnetic field to the soft magnetic layer. (For example, see U.S. Pat. No. 5,815,342) However, there is a fatal defect such that the magnetic field from the magnetic field generation device affects the magnetic head as a disturbance magnetic field with the result that the realization is difficult as a result.
An object of the present invention is to realize the stabilization of the magnetic domain state of the soft magnetic layer of the disk without affecting the special manufacture step and the magnetic head thereby attempting to decrease the magnetic noise and to realize stabilization with respect to the disturbance magnetic field.
The present invention provides a disk drive having a device which uses a double-layered structure provided with a soft magnetic layer on the lower layer of the magnetic recording layer, so that the magnetic domain of the soft magnetic layer is uniformed, the device generating a magnetic field for stabilizing the structure of the magnetic domain. That is, the disk drive comprises: a disk medium which is a double-layered data recording medium having a magnetic recording layer and a soft magnetic layer; a head for conducting a read/write operation of data with respect to the magnetic recording layer of the disk medium; an actuator for moving the head in a radial direction on the disk medium; and a device for applying a direct current magnetic field having an intensity of a predetermined magnetic field to the longitudinal direction corresponding to a horizontal direction in the case where the axial direction of the disk medium is set as a vertical direction.
In such a structure, the magnetic domain of the soft magnetic layer of the disk is uniformed without affecting the magnetic head and without requiring a special manufacture step, with the result that the stabilization of the structure of the magnetic domain can be realized. Consequently, with a method which allows the realization, the magnetic disk is decreased from the soft magnetic layer and the stability of the disturbance magnetic field can be secured. As a consequence, it becomes possible to promote the realization of the disk drive of the perpendicular magnetic recording method using, for example, the two-layer structure.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.